[1130] Utility of Phospho-Histone H3 in Problematic Uterine Smooth Muscle Tumors

Adriana M Doldan-Silvero, Carlos R Acevedo-Gadea, Deborah Z Stevens, Richard Cartun, Srini Mandavilli. Hartford Hospital, Hartford, CT; Yale School of Medicine, New Haven, CT

Background: Phospho-histone H3 (PHH3), a mitosis specific immunomarker, has been suggested as a robust way of evaluating mitotic index (MI) in neoplasms wherein MI is important in accurate classification. MI is a key histologic feature in classifying uterine smooth muscle tumors but there are several confounding factors. There is only one pilot study that suggested PHH3 as usefu in separating smooth muscle tumors of uncertain malignant potential (STUMP) from leiomyosarcoma (LMS). No studies have been done evaluating the PHH3 usefulness in other smooth muscle tumors such as cellular/mitotically-active and atypical/ bizarre leiomyomas (CL-BL) ocasionally difficult to separate from STUMP and LMS. The aim of this study was to evaluate the utility of PHH3 immunolabeling in a group of morphologically challenging smooth muscle tumors.
Design: 9 cases of CL-BL, 6 of STUMP and 5 of LMS (1 myxoid LMS) from 2000 to 2012, previously diagnosed using the presently accepted morphologic criteria, were retrieved from the archives of the Department of Pathology at Hartford Hospital. Representative H&E slides were reviewed, PHH3 immunohistochemical stains were performed and positivity scored by 2 pathologists in the hot spot areas of staining as # positive cells/ 10 HPF (PHH3 MI). The mean MI of each group (CL-BL, STUMP and LMS) was then calculated.
Results: See

Pathologic and immunophenotypic findings in the selected uterine smooth muscle tumors
 CL (n=9)STUMP(n=6)LMS (n=5)
MI0-10 mitoses/10HPF (mean: 1.8)0-10 mitoses/10HPF (mean: 4)3-15 mitoses/10HPF (mean: 10)
NecrosisAbsentAbsentPresent in 4 out of 5 cases
AtypiaMild (7) and moderate (2)Moderate (3) and severe (3)moderate (4) to severe (1)
PHH3 MI0-11 mitoses/10HPF (mean: 4)0-15 mitoses/10HPF (mean:6.5 )5-30 mitoses/10HPF (mean: 12)

Conclusions: There is excellent correlation between MI and PHH3 MI. The PHH3 immunoreactivity is easy to evaluate with mitotic figures readily identifiable making mitotic count more reliable, particularly in the CB-BL cases where degenerative atypia or apoptotic figures are prominent. These preliminary results suggest that a PHH3 MI standard could be established for categorization of problematic smooth muscle tumors. This could be useful in the gynecological pathology grey zone wherein accurate separation of CL-BL, STUMP and LMS remain challenging in routine practice as well as in low-grade LMS, myxoid and epitheliod smooth muscle tumors, wherein mitoses can be hard to find and diagnosis of malignancy difficult to establish.
Category: Gynecologic & Obstetrics

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 241, Tuesday Afternoon


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